1. Field of the Invention
This invention relates to fuel filters and pumps submerged in the sump of a fuel tank to ensure adequate fuel supply through the filter to prevent pump cavitation and to permit relatively quick and easy replacement of the filter element. It is particularly well adapted for use with fuel supply lines with an increased pumping capacity in automotive applications and more particularly for race cars.
2. Description of the Related Art
High performance street cars and race cars tend to have engines which produce over 500 horse power (HP) and even over 1000 HP. Engines capable of generating over 500 HP usually require high efficiency fuel pumps and filtering systems. Failure to provide a sufficiently efficient filtering system for a high efficiency fuel pump will result in the development of a vacuum or low pressure area at the inlet of the pump causing cavitation of the pump at normal operating temperatures resulting in a loss of fuel pressure and flow through the engine. Such operating conditions may also result in a build up of excess heat in the fuel pump due to friction, causing damage to or possibly failure of the fuel pump.
To ensure quality and efficient filtering in high performance or racing applications, the fuel filter is replaced or cleaned much more frequently than under normal driving conditions including possibly during a race. However, adequate safeguards must be in place to minimize leaks of the flammable and toxic fuel and ensure the safe operation of the fuel supply system. Therefore, there is a need for a fuel supply system which can combine high efficiency with very simple, quick and safe replacement of the filtering element and if necessary the fuel pump, especially in racing applications where the filtering element may be replaced often to ensure quality filtering. Currently available fuel supply systems do not adequately address all these high performance characteristics in one compact fuel supply unit.
The pressure drop across the fuel filter is indicative of its efficiency with the smallest pressure drop possible being preferred. The pressure drop across the filtering element may be reduced by increasing its surface area which for most filters may be accomplished by increasing the quantity of filter pleats. The remaining pressure drop in the filtering system is usually caused by narrow passageways in the fuel supply inlet and outlet.
One way to reduce the pressure drop in the filtering system is to submerge the filter into the reservoir or fluid supply tank. In race car applications, this means submerging the fuel filter in the fuel tank. However, submerging the fuel filter in the fuel tank requires additional safeguards to prevent fuel from leaking out of the tank when the filter is changed.
U.S. Pat. No. 5,607,582 to Yamazaki et al. discloses a Filter System for Liquids. It contains a round base subassembly with inlet and outlet openings for fluid supply and a round filter housing subassembly attached to the base. The base subassembly consists of a round plate or disc with inlet and outlet openings on its upper surface. An intermediate round disk is mounted on the upper surface of the disc of the base assembly with inlet and outlet openings formed in the intermediary disk. The disks can rotate around their common axes to bring their inlet and outlet openings into flow communication or misalign them to cut off fluid flow therebetween. The filter housing subassembly consists of a cylindrical sleeve with two flanges on both ends. A bottom flange of the housing is attached to the round base plate by bolts and the top flange is for attachment of a lid. A round filter unit may be inserted into the sleeve and held in place by the housing lid. A thin round rotatable disk with inlet and outlet openings is attached to the bottom surface of the filter unit which contains inlet and outlet openings as well. This pair of inlet and outlet openings on the bottom of the filter subassembly may be aligned or misaligned in the same way as in base subassembly. By rotating the filtering unit 90° and using a ‘pin in slot’ engagement between the filter housing subassembly and the base subassembly all four corresponding inlet and outlet openings may be brought into flow communication when the filter is in an operating state. By removing the housing lid and rotating the filter unit inside the housing 90° in an opposite direction, each pair of inlet and outlet openings in the base and filter housing subassemblies are misaligned or advanced to a closed position. With the openings in the base subassembly misaligned with the openings in the filter housing subassembly, the filter unit may be removed from the filter housing. The inlet and outlet openings of the separated filter unit will remain in a misaligned (closed) position during transportation for disposal, preventing leaks of fluid trapped inside the unit. In the same manner, the base subassembly shuts off the inlet and outlet openings therethrough until a new filter unit installed.
Since the filter assembly disclosed in the Yamazaki et al. '582 patent is installed in the fluid supply line, an unavoidable pressure drop in the inlet and outlet lines of the filter system will cause the same pumping problem for fuel supply systems as discussed above. Furthermore, the Yamazaki filter unit utilizes only one inlet opening and one outlet opening through the base and filter housing subassemblies, which restricts the fluid flow through the filter. The area of inlet and outlet openings of both subassemblies is limited since they must be significantly spaced apart in order to provide sufficient surface area for these openings to be rotated between aligned and misaligned positions.
U.S. Pat. No. 4,367,144 to Peters et al. discloses a filter including a cylindrical casing with fluid inlet openings extending therethrough proximate a distal end and fluid outlet openings extending therethrough proximate a filter inlet end. A removable filter element is slid into and out of the casing through an opening formed in the filter inlet end. Spring biased shutters are normally biased in a position extending over the fluid inlet and outlet openings. As a filter is slid all of the way into the casing it engages the spring biased shutters and advances them to an open position. Upon removal of the filter element from the casing for replacement, the shutters are urged by the springs back across and in a closed alignment with the fluid inlet and outlet openings to prevent the flow of fluid into the casing.
One drawback of the filter assembly of the Peters et al. '144 patent is that the if the shutters malfunction and become stuck in the open position, fluid can leak back out of the fluid sump, through the fluid inlet openings and out the open end of the filter housing. Such a malfunction can be particularly problematic if the filter is used for filtering fuel or other toxic or flammable liquids.
There remains a need for an efficient and safe filtering and pumping system for fuel supply and especially for racing and high performance applications.